Ένα μυρμήγκι ανέβηκε στο τραπέζι, αλλά το τσίμπημα που έχω στο χέρι μάλλον είναι από κουνούπι.

Because μυρμήγκι is a neuter noun in Greek. The indefinite article has to match the noun’s gender:

• ένας = masculine
• μία / μια = feminine
• ένα = neuter

So:

• ένα μυρμήγκι = an ant

The same thing happens later with το τσίμπημα, because τσίμπημα is also neuter.

Ανέβηκε is the aorist (simple past) form of ανεβαίνω = to go up / climb up.

So ένα μυρμήγκι ανέβηκε στο τραπέζι means the ant went up onto the table or climbed onto the table as a completed action.

This tense is used because the speaker is referring to a single finished event in the past.

Στο is a contraction of:

• σε = to / at / on / into
• το = the

So:

• σε + το = στο

Therefore:

• στο τραπέζι = on the table / onto the table

This is extremely common in Greek:

• στο σπίτι = at home / to the house
• στον φίλο = to the friend
• στην πόλη = in the city

In this sentence, it most naturally means onto the table.

Because ανέβηκε already contains the idea of upward movement, στο τραπέζι is understood as the destination. So the sense is:

• The ant climbed up onto the table

In English, on and onto are often distinguished more clearly than in Greek. Greek often relies on the verb to show the movement.

Τσίμπημα can refer to a bite, sting, or small prick/pinch, depending on context.

In this sentence, because of κουνούπι (mosquito), the natural meaning is:

• mosquito bite

So το τσίμπημα here is best understood as the bite.

Here που introduces a relative clause. It means that or which:

• το τσίμπημα που έχω στο χέρι
• the bite that I have on my hand

Greek που is very common and much simpler than English relative pronouns in some ways. It does not change form for gender or number here.

So:

• το βιβλίο που διαβάζω = the book that I’m reading
• ο άνθρωπος που είδα = the person that I saw

Greek often uses έχω in expressions where English might say I have or sometimes simply describe something as being somewhere.

So:

• το τσίμπημα που έχω στο χέρι literally = the bite that I have on the hand

In natural English, that becomes:

• the bite on my hand
• the bite I have on my hand

This is a very normal Greek way to describe something physically present on the body.

Greek often leaves out possessives like μου (my) when ownership is obvious from context.

Since the clause already says που έχω = that I have, it is clear that the hand is the speaker’s hand. So στο χέρι is enough.

If someone said στο χέρι μου, that would also be correct, but it would sound a bit more explicit.

So both are possible:

• που έχω στο χέρι
• που έχω στο χέρι μου

The version in your sentence is simply more economical.

Here μάλλον means probably or most likely.

So:

• μάλλον είναι από κουνούπι
• it’s probably from a mosquito

Be careful: μάλλον can also mean rather in other contexts.

For example:

• Μάλλον έχεις δίκιο. = You’re probably right.
• Θέλω μάλλον καφέ παρά τσάι. = I’d rather have coffee than tea.

In your sentence, the meaning is clearly probably.

Από usually means from, and here it shows source/cause.

So:

• είναι από κουνούπι = it is from a mosquito

That is the normal Greek way to say that the bite was caused by a mosquito.

You will see από used similarly in many cases:

• Πέθανε από καρκίνο. = He died of cancer.
• Έπαθα αλλεργία από κάτι που έφαγα. = I got an allergy from something I ate.

Both are possible, but they are not exactly the same in feel.

• από κουνούπι = from a mosquito / mosquito-related, more general
• από ένα κουνούπι = from a mosquito, with a slightly more specific or countable feel

In Greek, after από, the noun often appears without an article when the speaker is talking about the type or source in a general way.

So είναι από κουνούπι sounds very natural for it’s a mosquito bite.

Because the sentence talks about two different time frames:

• Ένα μυρμήγκι ανέβηκε στο τραπέζι → a completed event in the past
• το τσίμπημα ... είναι από κουνούπι → a present conclusion about the bite now

So the speaker is saying, in effect:

• An ant climbed onto the table, but the bite I have on my hand is probably from a mosquito.

This tense combination is very natural.

Yes. The sentence sets up a contrast:

• An ant climbed onto the table
• but the bite is probably from a mosquito

The word αλλά means but and marks that contrast clearly. The idea is that although an ant appeared, it probably was not the cause of the bite.

So αλλά helps connect the two ideas in a slightly corrective way.

Yes. Χέρι can mean hand but in everyday Greek it can sometimes refer more broadly to the arm/hand area, depending on context.

In this sentence, στο χέρι will usually be understood as on my hand or on my arm/hand area. English often forces a more exact choice than Greek does.

So the exact translation may vary slightly depending on the situation.